1. Technical Field
The present invention relates generally to contour measuring devices for coordinate measuring machines (CMMs); and more particularly to a contact-type contour measuring device with a relatively steady measuring force.
2. Description of Related Art
Manufactured precision objects such as optical components (for example, aspherical lenses) and various industrial components need to be measured to determine whether manufacturing errors of the objects are within acceptable tolerance. Manufacturing errors are the differences between design dimensions of the object and actual dimensions of the manufactured object. Precision measuring devices are used to measure the objects. Generally, the precision objects are measured with a coordinate measuring machine (CMM), which has a touch trigger probe that contacts the objects. A measuring force applied to the touch trigger probe of the CMM should be steady. If the measuring force is not steady, a relatively large measuring error may occur.
A typical method to reduce a measuring force on the touch trigger probe is to configure the touch trigger probe with a spring. An elastic force of the spring is regarded as a measuring force. However, when the contact tip moves along the surface of the object being measured, vibrations of the movement may cause the spring to resonate and deform. The measuring force varies with the deformation of the spring, and subject to errors in the measurement results.
Another probe uses an air pump to provide a measuring force. However, the air pump cannot provide a steady measuring force because the air pump provides pulsed pressure.
Therefore, a new contour measuring device is desired to overcome the above-described shortcomings.